Make new_suggestions and Send to Google Chat recoverable

MQ-167-01: a scheduled or manual batch now emits new_suggestions:{batchId}
in the transaction that first stores its Side quests, so the cards and
their notification commit together. A later round that fails, or a
failure recording the batch's end, no longer loses the event; a later
round's emit is a no-op by key; a notification that cannot be stored
fails that store, leaving no unannounced cards. Replenish batches still
never notify. finishBatch goes back to recording status only.

MQ-167-02: migration 0017 adds shopping_lists.chat_send_unconfirmed_at.
SendToChat records the send as begun before posting, clears it with
sent_to_chat_at once Google Chat accepts, and clears it alone when Chat
refuses. A post Chat does not answer, or one it accepts that cannot be
recorded, is ErrSendUnconfirmed (502 chat_unconfirmed, not retryable)
and leaves the marker, as does a crash mid-send; a repeat without resend
never reposts, and resend posts again. The Supply run screen re-reads
the list after a failed send, shows an unconfirmed send, offers no Retry
for it, and sends again only with resend.

Task: f0cd9d50-9c11-41be-a945-7bae9f5f28a4

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/db/querier.go

@@ -12,6 +12,10 @@ import (
 type Querier interface {
 	// An unknown id returns sql.ErrNoRows.
 	ArchiveDinner(ctx context.Context, arg ArchiveDinnerParams) (Dinner, error)
+	// Records a send of list id to Google Chat begun at
+	// chat_send_unconfirmed_at, before it is posted, unless the list is frozen
+	// into the Supply archive.
+	BeginShoppingListChatSend(ctx context.Context, arg BeginShoppingListChatSendParams) (int64, error)
 	// Leases the pending notification due longest ago by moving its
 	// next_attempt_at to lease_until, and returns it. A claimed row is not due
 	// again until the lease ends, so no other claim takes it while it is being
@@ -26,6 +30,8 @@ type Querier interface {
 	// sets last_sync_error, keeping the chosen calendar. Affects no row when
 	// nothing is connected.
 	ClearIntegrationsGoogleToken(ctx context.Context, arg ClearIntegrationsGoogleTokenParams) (int64, error)
+	// Clears the send of list id begun, once Google Chat refused it.
+	ClearShoppingListChatSend(ctx context.Context, arg ClearShoppingListChatSendParams) (int64, error)
 	// Drops references to the runs created before the cutoff, so the purge
 	// can delete them.
 	ClearSuggestionBatchAIRunsBefore(ctx context.Context, cutoff string) (int64, error)
@@ -235,8 +241,8 @@ type Querier interface {
 	// Records a delivered notification; updated_at is when it was sent. The
 	// lease must still be the claim's.
 	MarkNotificationSent(ctx context.Context, arg MarkNotificationSentParams) (int64, error)
-	// Records list id sent to Google Chat at sent_to_chat_at, unless it is
-	// frozen into the Supply archive.
+	// Records list id sent to Google Chat at sent_to_chat_at, its send
+	// confirmed, unless it is frozen into the Supply archive.
 	MarkShoppingListSentToChat(ctx context.Context, arg MarkShoppingListSentToChatParams) (int64, error)
 	// Records an edit of plan id, raising its revision: a synced plan becomes
 	// changed, any other keeps its status.